The present invention relates to a process for producing adamantane (tricyclodecane[3.3.1.13,7]) by isomerization reaction of tetrahydrodicyclopentadiene (tricyclodecane[5.2.1.02,6]) with a HF.BF3 catalyst. Adamantane is a very useful raw material for producing an adamantane derivative and is applied to specialty chemical and fine chemical fields including a druggery, special fuel, a lubricant, an engineering polymer, a functional polymer, an agrichemical and a surfactant.
Generally, adamantane is obtained by isomerization of tetrahydrodicyclopentadiene. Conventionally, as a catalyst used for producing adamantane, there are known aluminum halide type catalysts, alumina type catalysts, zeolite type catalysts and superacid catalysts.
When the aluminum halide type catalyst such as AlCl3-HCl, AlBr3-t-BuBr, AlCl3-t-BuCl is used, the amount of the catalyst based on a raw material is required to increase. Further, a byproduct compound formed by the reaction is apt to form a strong complex with the catalyst. Therefore, defects are that an activity decreases immediately and that the renewal of the catalyst is difficult. Journal of Brennst-Chem. 1961, 42, 90, describes a method in which a reaction is carried out by using HCl-AlCl3 catalyst under high hydrogen pressure. In this system, high pressure hydrogen is required and many problems are found with regard to the recovering method of a catalyst.
Further, alumina support catalysts such as chlorinated platinum - alumina and sulfuric acid-treated silica - alumina have a low activity and the lifetime of these catalysts is short.
As a method of highly selectively obtaining adamantane, conventional methods include the use of a rare earth element-exchanged zeolite catalyst, trifluoromethanesulfonic acid (CF3SO3H), trifluoromethanesulfonic acid-antimony pentafluoride (CF3SO3H+SbF5), trifluoromethylsulfonylboron (B(OSO2CF3)3) and the like.
For example, JP-A-60-246333 discloses a method in which a cation exchange zeolite supporting an active metal such as platinum is used. In this method, an active metal is used as an isomerization catalyst, and when the unmodified zeolite supporting an active metal is used, a ring opening reaction by hydrogenation occurs so that a treatment with ammonium sulfate or the like is required, i.e., a preparation method is complicated. With regard to reaction results, the selection rate is low or approximately 50%, and the yield is low or approximately 40%.
Further, the use of a catalyst such as CF3SO3H+SbF5 or CF3SO3H+B(OSO2CF3)3 described in J.org. Chem., 1986, 51, 5410-5413, can give adamantane highly selectively, while the problem is that the handling and recovery of a catalyst are difficult.
On the other hand, when a HF.BF3 type catalyst which is a kind of superacid catalyst is used, it is known that adamantane can be obtained at a high yield of 60% or higher as proposed, for example, in JP-A-50-35151.
The HF.BF3 type catalyst is excellent in handling properties and recovery of a catalyst and can give adamantane at high yields. However, the selection rate of adamantane is approximately 60 to 75%. In a process using a superacid such as a HF.BF3 type catalyst, a high cost is required for separation and purification so that an increase in selectivity is highly advantageous. It is desired to increase the selectivity further.
It is an object of the present invention to provide a process for producing adamantane (tricyclodecane[3.3.1.13,7]) by isomerization reaction of tetrahydrodicyclopentadiene (tricyclodecane[5.2.1.02,6]) with a HF.BF3 catalyst which process gives an intended adamantane at a high selection rate.
That is, the present invention is directed to a process for producing adamantane (tricyclodecane [3.3.1.13,7]) by isomerization reaction of tetrahydrodicyclopentadiene (tricyclodecane[5.2.1.02,6]) with a HF.BF3 catalyst, which process is characterized in that the reaction is carried out in the presence of at least one metal selected from the group consisting of the group 8 metals, the group 9 metals and the group 10 metals of the periodic table and hydrogen.
The present inventors have made diligent studies for overcoming the above problems and have found that at least one metal selected from the group consisting of the group 8 metals, the group 9 metals and the group 10 metals of the periodic table is added to an isomerization reaction system with a HF.BF3 catalyst under a reduction atmosphere, whereby adamantane can be highly selectively produced at high yields. On the basis of the above finding, the present invention is reached.
The metal used in the present invention is at least one metal selected from the group consisting of the group 8 metals, the group 9 metals and the group 10 metals of the periodic table, such as Fe, Co, Ni, Cu, Ru, Pd, Ir and Pt. In particular, palladium, platinum and nickel may be preferably used. For preferable uses thereof, these metals may be on a support. Preferable examples include platinum/activated carbon, palladium/activated carbon, or the like.
The reaction conditions of the present invention are as follows. 0.5 to 10 parts by weight, preferably 3 to 4.5 parts by weight, of HF, 0.25 to 1.5 parts by weight, preferably 0.5 to 1.3 parts by weight, of BF3 and 0.0001 to 0.001 part by weight, preferably 0.0003 to 0.0007 part by weight, of the above metal are used per 1 part of tetrahydrodicyclopentadiene. Further, hydrogen is used so as to achieve a partial pressure of 0.1 to 5.0 Mpa, preferably 0.5 to 2.0 Mpa, whereby a reduction atmosphere is obtained. The reaction temperature is 0 to 120xc2x0 C., preferably 40 to 80xc2x0 C. The reaction pressure is 0.6 to 7.0 Mpa, preferably 1.1 to 3.5 Mpa.